That depends on the trip and on the number of people travelling with you.
There are nine types of tickets: the day pass, the Plus Card, the advantage card, a regular ticket, a Lijnkaart, a Lijnkaart %, a group ticket, a pass and an SMS ticket. The ticket clerk is a specialist and can help you find the most suitable and cheapest formula.
More information about our fare system (e.g. about free use of bus or tram) can be found on the general website of De Lijn.
Purchase your ticket in advance. This is at least 20% cheaper than on the vehicle.